| Sedimentary basins are created at different stages of plate evolution, either divergent or convergent, so they are closely related to the three known types of Plate boundaries. Knowing the tectonic background under which, basins formed helps determining their geomechanical natures (extensional, compressional and shear) in each developmental phase and full understanding of the sedimentologic character and geothermal evolution of the basin. In this case during Paleozoic, nearly east west trending arc structures resulted from the interaction between China Plate and Siberian Plate. In Mesozoic the westward subduction of Kula-Pacific Plate under the China Continental Plate resulted in the NNE and NE trend structures (Duimadao fault, Diaoyudao fault, Okinawa fault, uplifts belts and subsidence belts) as well as volcano-magmatic belts in eastern of China plate. These NNE and NE faults become a long transform fault system and formed a boundary between the eastern margin of China Continental Plate and Philippine Sea Plate. This system plays an important role in the relative movement between the West Pacific Plate and Eurasian continental Plate. Thus, the Paleozoic structures had been modified. During late Mesozoic and Cenozoic, extensions were widespread in Eastern China and adjacent areas. The induced compressions and extensions, uplifting and subsidence as well as large -scale magamatism, increased the pre-existing NE-NNE trending faults, uplifts and subsidence belts. This is how; the giant transform structure led to the formation of Xihu Depression. It is a Late Cretaceous to Tertiary basin located on the Eastern part of the continental shelf of the East China Sea; it occupies an area of 59,000 km2. It is bounded by longitude of 124o30' to 127o00' and latitude of 28o30' to 31o00.Having known the geologic and tectonic background of Xihu Depression, to evaluate the play, to reconstruct the burial history of the basin and build thermal andmaturity models, and subsequently to establish possible petroleum systems become a routine task.Play evaluation can be viewed as a separate level of investigation in an exploration program. Play investigations describe the present-day geologic similarities of a series of present-day traps. On the other hand petroleum system includes a pod of active source rock and all related oil and gas, and all the essential elements and processes needed for oil and gas accumulations to exit. The essential elements are source rock, reservoir rock, seal rock and overburden rock, and the processes include trap formation and the generation-migration-accumulation of petroleum. While basin modeling is the term most often used to describe the modeling of a series of processes that deal with maturation, generation, expulsion, migration, trapping and to some extent preservation of hydrocarbons. This approach includes components of both basin modeling and petroleum system modeling. Petroleum system modeling attempts to recreate the history of hydrocarbons within a specific system. Basin modeling often considers several petroleum systems simultaneously in a basin.In our case study of Xihu Depression, we carry out one-dimensional basin modeling that simulates burial, maturation, generation and expulsion histories using four wells as control and one seismic line 93QY4. Different models have been built and tested against measured vitrinite reflectance and temperature from Baoyunting-1, Yuquan-1, Pinhu-5 and Duanqiao wells to make sure the final results fit the geologic model. We come up with the results as such the best model (close to the geologic reality) is that of Transient Heat Flow, Pinghu Formation is the main source rock with high hydrocarbon generation efficiency, Huagang Formation as reservoir, and Pinghu-Huagang (!) as the most important petroleum system in the basin. It is also observed that there is a fair to good match from the simulated vitrinite reflectance (Ro) and temperature values to the measured Ro and temperatures values in all four wells. However the relationship bet...
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